As window glass intended for vehicle, a glass (smart glass) capable of electrically switching transmittance of light by on/off of a power supply switch has been known. As a functional material used for such a smart glass, there is a suspended particle device (hereinafter sometimes referred to as “SPD”) film.
The smart glass is fabricated by sealing, for example, the SPD film in a laminated glass made by bonding glass plates with an intermediate bonding layer. In this event, for the purpose of protecting an end portion of the SPD film, the SPD film is cut into a size smaller than the sizes of the glass plates and the intermediate bonding layer and sealed in the laminated glass in a manner that the end portion is covered with the intermediate bonding layer. Specifically, the general configuration is that an intermediate bonding layer in a frame shape is arranged at a peripheral portion of the SPD film, the SPD film and the intermediate bonding layer are sandwiched between two intermediate bonding layers, and the two intermediate bonding layers are further sandwiched between a pair of glass plates.
However, even if the SPD film is sealed in the laminated glass as in the above, heat and moisture intruding from an end face of the laminated glass reach the end portion of the SPD film via the intermediate bonding layer, or the end portion deteriorates due to influence of a plasticizer contained in the intermediate bonding layer, resulting in a problem of becoming impossible to switch the light transmittance in response to on/off of the power supply switch at the end portion.
As means for preventing deterioration of the end portion of the SPD film sealed in the laminated glass, several techniques are suggested. For example, Patent Reference 1 (JP-A 2009-534283) describes a technique of using an intermediate bonding layer made of a material free from a plasticizer such as an ethylene-vinyl acetate copolymer resin in order to prevent intrusion of the plasticizer from the intermediate bonding layer. Further, Patent Reference 2 (JP-A 2013-505188) describes a technique of drying a constituent material of an intermediate bonding layer including an intermediate bonding layer in a frame shape to reduce the moisture content before fabrication of the laminated glass in order to suppress moisture intruding from the intermediate bonding layer in a frame shape.